Existing forging processes for the manufacture of compressor and turbine wheels rely on open die forging. Open die forging processes require additional input material tonnage and more heat treatment, and more forging processing steps.
Current closed die forging processes involve higher press tonnages. The use of closed die forging requires investments of higher capacity presses. However, there are currently no high capacity presses suitable for economical closed die forging of turbine and compressor wheels and turbine spacer wheels formed, for example, of CrMoV and NiCrMoV.
U.S. Pat. No. 6,240,765 discloses a closed die forging process including a die set having a stationary die and a movable die in facing-but-spaced-apart relation to the stationary die along a press access and defining a work piece volume therebetween. U.S. Pat. No. 6,240,765 starts with a workpiece geometry which covers the entire plan view area of the dies. As the workpiece covers the entire plan view area of the dies, the strain rates to be used are much lower which results in frequent heat treatment steps between the various incremental forging steps. The process of U.S. Pat. No. 6,240,765 therefore requires greater input material tonnage.